Scientists Calculate Rate of New Star Formation and Decline
(Photo : D. Sobral)
For the first time, a team of international researchers has established the rate of formation of new stars in the Universe. The group found that the rate of formation of new stars in the Universe is now only 1/30th of its peak and that this decline will continue.
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According to the model for the evolution of the Universe, stars began to form some 13.4 billion years ago, or around three hundred million years after the Big Bang. These first stars were considered as hundred times more massive than our sun. Such massive stars age very fast and explode into supernovae within a million years. Whereas the lower mass stars in contrast have much longer lives and last for billions of years.
Dust and gas from stellar explosions is recycled to form newer generations of stars. Irrespective of the mass and properties, stars are important elements of galaxies like our own Milky Way. In order to understand how galaxies form and evolve, it is important to know the history of star formation across cosmic time.
In the current study, with the help three telescopes spread over the world viz the UK Infrared Telescope (UKIRT), the Very Large Telescope (VLT) and the Subaru telescope, the scientists carried out a complete survey ever made of star-forming galaxies at different distances, with around ten times the data of any previous effort.
With the range of distances, the time taken for light to reach us indicates that we can see identically selected galaxies at different periods in the history of the universe so we can really understand how conditions change over time.
By looking at the light from clouds of gas and dust in these galaxies where stars are forming, the team was able to assess the rate at which stars are being born. They found that the production of stars in the universe as a whole was continuously declining over the last 11 billion years, being 30 times lower today than at its likely peak, 11 billion years ago.
Dr. David Sobral of the University of Leiden in the Netherlands comments: "You might say that the universe has been suffering from a long, serious 'crisis': Cosmic GDP output is now only 3 percent of what it used to be at the peak in star production!"
'If the measured decline continues, then no more than 5 percent more stars will form over the remaining history of the cosmos, even if we wait forever. The research suggests that we live in a universe dominated by old stars. Half of these were born in the 'boom' that took place between 11 and 9 billion years ago and it took more than five times as long to produce the rest. The future may seem rather dark, but we're actually quite lucky to be living in a healthy, star-forming galaxy which is going to be a strong contributor to the new stars that will form, " he added.
The team published their results in the journal Monthly Notices of the Royal Astronomical Society.